Tetanus as Cause of Mass Die-off of Captive Japanese Macaques, Japan, 2008

Tomomi Nakano, Shin-ichi Nakamura, Akihiko Yamamoto, Motohide Takahashi, and Yumi Une

Author affiliations: Azabu University, Kanagawa, Japan (T. Nakano, S. Nakamura, Y. Une); and National Institute for Infectious Diseases, Tokyo, Japan (A. Yamamoto, M. Takahashi)

Abstract

In 2008 in Japan, 15/60 captive Japanese macaques died. Clostridium tetani was isolated from 1 monkey, and 11 had tetanus-specific symptoms. We conclude the outbreak resulted from severe environmental C. tetani contamination. Similar outbreaks could be prevented by vaccinating all monkeys, disinfecting housing areas/play equipment, replacing highly C. tetani–contaminated soil, and conducting epidemiologic surveys.

Tetanus is a wound infection caused by a potent neurotoxin produced by Clostridium tetani. The bacterium is difficult to isolate, and no pathologically characteristic lesion is present during infection; thus, tetanus diagnosis is based on tetanus-specific clinical symptoms (1–4). Tetanus is a highly lethal zoonosis, and cases usually occur sporadically. Outbreaks among humans have occurred only after earthquakes and tsunamis (4). We report on an outbreak of tetanus in 2008 among a captive colony of Japanese macaques (Macaca fuscata) in Japan.

The Study

Figure 1

Thumbnail of Number of deaths during 2006–2009 among macaques (Macaca fuscata) housed in an animal facility in the Kantou area of Japan. Grey boxes, monkeys with tetanus-specific clinical symptoms; white boxes, monkeys without tetanus-specific clinical symptoms. 1, January–March; 2, April–June; 3, July–September; 4, October–December; n, total number of monkeys. *Juvenile animal; †Accident at time monkeys captured for vaccination (death due to hyperthermia).

Figure 1. . . Number of deaths during 2006–2009 among macaques (Macaca fuscata) housed in an animal facility in the Kantou area of Japan. Grey boxes, monkeys with tetanus-specific clinical symptoms; white boxes,...

In 2008, deaths suddenly increased among Japanese macaques housed in a facility in the Kantou area of Japan. At that time, the facility, which had been in service for >40 years, housed ≈60 macaques, 15 (25%) of which died. This mortality rate was much higher than that during 2006 (10.9%, 7/64 monkeys), 2007 (7.1%, 4/56), 2009 (13.8%, 9/65), 2010 (5.2%, 3/58), and 2011 (5.7%, 4/70) (Figure 1). A total of 42 monkeys died during 2006–2011, and investigations at the time of death showed that 14 of the monkeys had tetanus-specific symptoms: 1 of 4 that died in 2007, 11 of 15 that died in 2008, and 2 of 9 that died in 2009). Nine of the 11 monkeys that died with characteristic symptoms of tetanus in 2008 died during the breeding season (November and December). Thus, the observed number of presumed tetanus cases during the 2008 breeding season (9/60) was 8.4× greater than the number during the 2007 breeding season (1/56).